The present invention relates to a system for characterizing a liquid, comprising a sensor for providing an electrical output signal depending on a characteristic of the liquid, and a processing unit for processing the output signal of the sensor to obtain characterizing data of the liquid, and to methods for characterizing a liquid.
Known systems and methods for characterizing a liquid need the use of sophisticated devices which usually are designed for a single purpose, e.g. detecting specific ions in the solution. Such a system and method are for example disclosed in WO 98/39648. Devices to be used for determining characteristics of a solution, by immersion thereof in the liquid, are known from this document. Such devices are developed for specific purposes, e.g. measuring the temperature, or measuring the pH value of a solution. This implies that, for determining several characteristics of a solution, many different devices must be used in this known system. When, besides measuring characteristics of a liquid, some characteristics of a liquid have to be changed, e.g. if the temperature must be increased, until now separate devices were used for performing these actuating operations. This had the disadvantage that measures had to be taken so as to be able to immerse several devices in the liquid.
The present invention aims to provide an improved system and methods for characterizing a liquid of the above-mentioned type. Further, the invention has the object to provide a sensor with which different chemical and physical characteristics of a liquid can be measured and/or actuated.
According to the invention the system is characterized in that the sensor is made as a single sensor/actuator device, wherein means are provided for connecting the sensor/ actuator device in a plurality of manners to the processing unit, wherein in at least a part of said plurality of connecting manners the processing unit is adapted to actuate the sensor/actuator device and to process the output signal of the sensor/actuator device to obtain different characterizing data of the liquid.
According to the invention bleach activity can be determined in a liquid, in particular a washing liquid, wherein a varying voltage is applied to the liquid through a working electrode and a counter electrode, wherein the current through the liquid is measured as a function of the varying voltage and the peak current value is determined, wherein the bleach activity is derived from the peak current value.
According to a further aspect of the invention ion concentrations in solution are determined by measuring the conductivity of said solution as a function of temperature, and deriving the ion concentrations from the measured values of conductivity and temperature.